SRM Wireless Power Meter Dura Ace 172.5Shimano DuraAce 7800 10 speed compact crank: Cranks are available in lengths of between 165 and 180mm Chain rings:Bolt circle diameter: 130mmChain ring: 39/53 Other chain ring combinations might be available on request Weight: 919g with cranks, chain rings and bottom bracket (98 g)Bottom Bracket: DuraAce FC-7800 (weight: 98 g) not included in deliveryCompatible with PowerControl VI wireless and via SRM sensor cable with PowerControl IV and V.